ZOOLOGY AND BOTANY, MTCROSCOPY, ETC. 783 



symmetrical, irregularly lobed testes are placed dorsally in the hinder 

 part of the animal. Their vasa deferentia unite in due course to form 

 an ejaculatory duct, whose first portion acts the part of a seminal 

 vesicle. Neither cirrus-pouch nor intromittent organ are present. 



The female organs are — the ovary and oviduct, the vitellaria, the 

 shell-gland, the canal of Laurer and the " uterus." The unpaired 

 many-lobed ovary, somewhat dorsal in position, lies to the right of the 

 ventral sucker. The conical continuous oviduct has its narrow end 

 directed towards the shell-gland ; where the oviduct ends the uterus 

 begins. The paired vitellaria are made up of (a) the vitellarian 

 glands, (b) their longitudinal collecting sinuses, (c) the two transverse 

 ducts passing from these, (d) the rather long pear-shaped reservoir 

 into which the transverse ducts debouch and (e) the yolk-duct proper 

 into which it is continued. The shell-gland, a dense cluster of uni- 

 cellular glandules, with interposed connective tissue, invests the 

 innermost section of the uterus, where the yolk-duct and oviduct by 

 their junction give rise to this conduit. Here also Laurer 8 canal 

 arises; making two or three convolutions in its course it at length 

 reaches the dorsal surface, where in the middle line its funnel-shaped 

 opening appears, just in front of the transverse vitellarian ducts. A 

 receptaculum seminis is appended to Laurer's canal not far from its 

 junction with the uterus. The beginning of the uterus, hidden amidst 

 the substance of the shell-gland and receiving the three ducts already 

 mentioned, constitutes the " ootyp " of the elder Van Beneden, a term 

 which Dr. Herbert would extend to the adjoining part of the long 

 winding tube which follows. The coiled vestibular portion of the 

 uterus wholly occupies the space below the transverse vitellarian duct, 

 on one side of the body, between the left diverticulum of the gut and 

 the middle plane. Thus from the genital sinus we pass, by way of 

 the uterus, to all the other female organs, and the whole gynasceuni 

 has two openings, — a ventral, leading into the sinus, and a dorsal 

 belonging to Laurer's canal. The minute structure of the parts 

 which make up this complex of glands and passages is described with 

 very great clearness. The share taken by each in the formation or 

 protection of the ova is also explained. 



Against the possibility of self-fertilization among trematodes Dr. 

 Kerbert urges many considerations. An internal vas deferens cannot 

 be said to exist. The road by the uterus is not favourable to the 

 transfer of spermatozoa. Most helminthologists, except Sommer, 

 regard Laurer's canal as a vagina, which it is in the strictest sense, — 

 an organ for copulation but not for parturition. The frequent occur- 

 rence of trematodes in pairs, the conformation of the body by which 

 the back of one individual is closely applicable to the ventral surface 

 of another, the position of the two external sexual orifices (equidistant 

 in Dr. Kerbert's fluke from the anterior sucker), the presence of 

 spermatozoa in Laurer's canal and their absence from the genital 

 sinus or uterine coils — these are facts which at present favour the 

 view, that the trematodes, if hermaphrodite morphologically, resemble 

 snails and most monoclinous flowering plants in not being self- 

 fertilizing. 



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